of milwaukee



Nov. '9 1926.

H. J. WIEGAND CAPACITANCE CONTROL DEVICE Filed May 29, 1922 ATTORNEY.

Patented Nov. 9, 192-.

UNITED STATES PATENT HENRY J. WIEGAND, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLER-HA1? MEI} MFG. 00., OF MILWAUKEE, WISCONSIN, A. CORPORATION OF VJISCQNSIN.

CAPACITANCE-CONTROL DEVICE.

Application filed May 29,

service.

Another object is that of providing a variable condenser of materially increased capacitance range and, minimized space requirements.

Another object is that of providing such a condenser adapted to provide exceedingly close and accurate capacitance regulation Without necessitating fine or delicate adjustment of its operating parts.

a device comprising few, simple, durable and readily constructed parts compactly and conveniently arranged and capable of ready assembly.

Other objects and advantages will here nafter appear.

In the accompanying drawing wherein 1s illustrated a preferred embodiment of the invention,

Figure 1 is a vertical sectional view thereof, certain portions, however, being shown in elevation; while,

Fig. 2 is also a vertical sectional view, substantially on line 2-2 of Fig. 1.

Referring to the drawing, the condenser illustrated comprises essentially a plurality of juxtaposed conductive elements insulated from one another and provided with connections alternately to opposite sides of the controlled circuit, said elements being relatively adjustable to bring different values of surface area thereof into capacity relation with one another.

In practice such elements as well as the insulating medium therebetween, are preferably curved, whereas at least one of said elements is flexible and preferably of some resiliency, thereby permitting different portions thereof to be brought progressively into proximity to the other element or elements, while preserving a bias or tendency of the elements to separate one from another unless positively held.

' I the drawing a single pair, 5 and 6, of

155 names e a a a c in comparat ve 1 99- Another object is that of providing such 1322. Serial No, 56%,312.

tentially co-oper ative capacity relation to one another and are maintained permanently and positively insulated by means of a relatively thin dielectric 7 preferably solid in character. The element 5 having the dielectric 7 wrapped thereabout is curved cy-' lindrically and mounted upon a drum 8 for axial rotation or oscillation. A terminal portion of the element 6 is permanently secured to a peripheral portion of such cylindrical structure. The remainder of said element 6 is so disposed and held that upon rotation of such cylinder in one direction said element 6 is caused to wrap thereabout to an extent determined by the extent of such turning, whereas reverse rotation of the cylinder serves to produce an opposite effect.

Obviously the effective capacitance of the de-.

vice for any given setting thereof is a function of the area of the adjacentsurfaces of the two elements thus caused'to approximate one another. A

In practice the flexible element 6 may conveniently be carried by and wrapped about asecond drum 9 supported in proximity to the drum 8, the relation being preferably such that as the drum 8 isrotated in either direction the drum 9 is constrained to rotate also but in the opposite direction.

In practice said drums 8 and 9 are preferably rotatably carried by individual shafts 10 and 11 Which in turn are mounted within or upon a suitable U-shape-d frame member 12. Said frame may in practice be screwed or otherwise secured to a panel 13 or other vertical or horizontal support. The shaft 10 is adapted to penetrate the frame 12 and also preferably the support 13 and may carry beyond the latter a suitable knob 14 or other operating device. A set screw 15 provides for clamping the shaft 10 within the drum 8 in angularly and axially adjustable relation.

The drum 8 may preferably comprise a section of fibre tubing or the like clamped between a pair of circumferentially flanged end caps 16, 17 the latter being mounted upon a hub 18 and permanently secured thereto by spinning, 'swaging or the like against suitably disposed shoulders of the latter, said hub being in turn mounted directly upon the shaft 10 and secured thereto as aforedescribed. V

The element 5 is wrapped or otherwise assembled about the drum 8 and secured thereto by cementing or otherwise, i being spaced and insulated from the end caps thereof by the material of said fibre annulus. The dielectric 7 is similarly wrapped or otherwise assembled about the cylindri cal element and similarly secured thereto, as by cementing.

A terminal portion of the flexible element 6 is likewise secured to the outer surface of said dielectric as by means ofv screws 19 penetrating the material of the annulus and suitably insulated from the surrounding element 5 substantially as illustrated.

The drum 9 may be constructed substantially similar to the drum 8 aforedescribed but maybe preferably reduced. in size for reduction of space requirements. Also in this instance a pair of spaced hub sections 18 and 18 are provided and may be free to rotate upon a common shaft 11 which latter may comprise a fixed stud or pinion as shown. The opposite end of the flexible element 6 may be screwed directly to the insulating annulus of the drum 9.

As shown particularly in Fig. 1, the element 6 is preferably made considerably narrower axially than is the element 5, whereas the width of the dielectric 7 is at least substantially equal to that of the element 5, thereby providing against surface leakage from one conductive element to the other.

In practice the drum 9 is preferably biased as by spring to rotate in a direction to wind the element 6 thereon, such bias, however, being normally counteracted by means of a resilient frictioning member 21 mounted upon the frame and. bearing againstthe adjacent end cap 17 of drum 8, whereby the movable parts are adapted to remain stationary unless positively moved but upon unwrapping rotation of the drum 8 the spring 20 is adapted to act automatically for winding the unwrapped portion of the element 6 about the drum 9.

The elements 5 and 6 may be composed of thin sheet brass, phosphor bronze or other conductive 'material having the desired characteristics, whereas the dielectric '1' may comprise thin bakelite or other of the well known insulating substances or may even be composed of paper, preferably coated and impregnated with an insulating substance as for example parafline.

Vhile the condenser as aforedescribed is capable of ready adjustment to provide relatively small capacitance variations, it is nevertheless in many instances desirable to provide for still more close capacitance adjustment and to such end a Vernier adjustment condenser may be advantageously combined with the elements hereinbefore de scribed.

Such Vernier adjustment device may conveniently comprise an indepei'idently operable condenser, mounted within the frame 12 and corresponding in all or most essential respects to the construction just described except for being of much reduced axial dimensions.

In practice the drum 8 of such vernier adjustment condenser is preferably mount ed upon an individual shaft 10 which may preferably extend within and through the hollow shaft 10 and its operating knob 14:, said shaft being provided with an individual operating knob 14 or the like,

The vernier adjustment drum 9 may be mounted directly upon the stud 11 but capable of rotation thereon independently of the main condenser drum 9. The structure of the individual parts of such Vernier device may be in all essential respects similar to that of the corresponding elements of the main condenser except for the aforementioned reduction in axial extentof the .vernier adjustment elements, whereby no further description of such latter elements is required.

The necessary circuit connections for the aforedescribed parts may be conveniently effected substantially in the manner illustrated, that is to say the outer faces of the drum 8 are provided respectively with pairs 22 and 23 of collector rings insulated from said drum and from one another. The collector rings of each of the aforedescribed pairs are electrically connected with one another as by through bolts 24 whereas the pair of collector rings AS are also electrically-connected with the elements 5 and 5* of the main and vernier adjustment condensers and the collector rings are similarly connected electrically with the elements 6 and 6 of the condensers. In practicesuch conuections to the designated elements of the main condenser may comprise resilient contact fingers 25 and 26 having parts to engage the respective collector rings.

Additionally the frame 12 is provided with terminal studs 27 and 28 penetrating the same but insulated therefron'i said studs carrying within the frame resilient contactors 29 and 30 adapted to electrically engage the left hand collector rings 23 and 2.2 respectively, the foregoing elements pro viding suitable circuit terminals for the de-- vice.

Obviously where the vernier adiustnient elements are not employed the right hand set of collector rings may be mounted di rectly upon anc. in insulated relation to frame 12 and permanently elect... cally connected with the respective terminal studs and 28, the flexible cont-actors 25 and. heing then adapted to make circuit with said rings precisely as in the construction specifically described and illustrated.

Obviously the specific capacitance of the aforedescribed condenser may be predetermined at will by preselection of the axial width of its conductive elements. Also it is Ion apparent that the rate of capacitance varia tion for given ranges of operation of the device may be varied by varying the width of one or both of the conductive elements throughout different portions of the circumferential length thereof, whereby the curve representing the relation of capacitance change to turning angle may be caused to assume practically any desired shape. It is to be 'noted that with the conductive elements of uniform width as illustrated the aforementioned curve will be substantially a straight line, indicative of the operative characteristics which are ordinarily to be preferred.

The aforedescribed device when employed in radio apparatus has been found to be practically free from so-called body capacity effects which are objectionably characteristic of most types of variable condenser. Such amelioration of this objectionable feature is so pronounced that in practice it has been found possible to construct the supporting frame, operating shafts, etc., except the op erating handles, of metal and to operate the device manually without giving rise to any such objectionable effects.

\Vithout limitation to any particular theory to account for such marked improvement in operation, it is believed that the extremely close juxtapositioning of the 00'- operating conductive elements permits the intermediate charge to concentrate therebetween to an augmented degree and minimizes the extent to which said charge exists in the surrounding media.

lVhat I claim as new and desire to secure by Letters Patent is:

1. In a variable condenser, in combination, a pair of independently rotatable drums each having a peripherally carried conductive sheet and a dielectric sheet surrounding said conductive sheet and held in intimate contact therewith, additional individual conductive sheets for each of said drums having a terminal portion secured flatwise to said respective dielectric sheets, means for rotating said drums selectively to cause said last mentioned conductive sheets to wrap about the other sheets on the respective drums to an extent determined by the angle through which the drums are turned, individual tensioning means for forcing said additional conductive sheets into intimate contact with the respective dielectric sheets upon such rotation of the drums, slip rings carried by one drum and electrically connected respectively with the corresponding conductive sheets of both drums, and fixed terminal means for said rings.

2. In a variable condenser, in combina winding said second sheet thereon and means to act upon said first mentioned drum for overcoming such bias.

3. In a variable condenser, in combination, a pair of independently rotatable drums each having a peripherally carried conductive sheet and a dielectric sheet surrounding said conductive sheet and held in intimate contact therewith, additional individual conductive sheets for each of said drums having a terminal portion secured fiatwise to said respective dielectric sheets, means for rotating said drums selectively to cause said last mentioned conductive sheets to wrap about the other sheets on the respective drums to an extent determined by a the angle through which the drums are turned, individual tensioning means for forcing said additional conductive sheets into intimate contact with the respective dielectric sheets upon such rotation of the drums and tending to rotate said drums in a'reverse direction, and means frictionally engaging said drums to hold the same in their respective adjusted positions against the action of said tensioning means.

4 In a variable condenser, in combina tion, a pair of axially alined independently rotatable drums of relatively large and relatively small axial dimensions respectively, each of said drums having a conductive sheet permanently secured thereto peripherally and a dielectric sheet surrounding each conductive sheet and held in permanent contact therewith, additional conductive sheets for each of said drums having a terminal portion secured flatwise to the respective dielectric sheets, individual tensioning means for said additional conductive sheets tending to maintain the latter unwound from said drums, and means for frictionally holding either or both of said drums in different ro- HENRY J. WIEGANDI 

